Planet hunters have found hundreds of exoplanets, but none just like Earth

By Stephen Ornes, 17:45 PM February 22, 2012

Once upon a time — about 20 years ago — kids in school learned about nine planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. The Nine orbited the sun, and they were the only planets that mattered. Any others existed in the imagination of children or in science fiction books and movies. The Star Trek crew, for instance, regularly visited distant worlds populated by aliens. And the good guys in Star Wars fled to forested or icy planets to escape the bad guys in a...